What are good close up lenses compatible for a Nikon D3100?

I'm looking to buy a new lens that is good for close up photography. I'd really like to capture a lot of detail in my images

I was wondering what lenses would be good for such photographs and are compatible with the Nikon D3100.
It would also be nice if you could explain the circumstances in which the lens would be used (e.g. How close or far from the subject I would have to be)
Also, if you could mention the pros and cons to the lenses, that would be greatly appreciated.

Price would also be a factor in my decision, quite frankly.

Micro-Nikkor AF-S 60mm f/2.8 G
Reviewed at
http://www.photozone.de/...kkor_60_28
It will autofocus with your D3100. (Don't buy the premise that you won't miss autofocus.) It gets high marks for sharpness. The focal length is useful for portraits, too.
It is less expensive than the Micro-Nikkor AF-S 105mm f/2.8G IF-ED VR.

However the 60mm does lack VR, and the working distance is short for photographing live insects.

Macro lenses are not cheap. Below $400 you won't get any, and the good ones cost $550 or more.

As a long macro lens, good for shooting living insects, consider the Tamron 90mm
http://www.bhphotovideo.com/..._8_Di.html
It wouldn't be my choice though, but it's the cheapest among the longer macro lenses. Ignore what is written about using it for portraits, that applies to it when it's being used on full frame cameras (unless you have candids in mind). Be aware that there are versions of it without autofocus motor as well, which you do not want.

Other than that, as a short macro lens that is not good for insects but can be used for portraits, the Micro Nikkor 60mm/2.8G (not D!) gets my vote. It costs some $550, but currently it's more expensive due to the disaster in Japan. Generally it's not a good time to buy lenses right now for that reason.